Method and apparatus for treating sleep apnea

ABSTRACT

An oral appliance provides electrical stimulation to a patient&#39;s tongue in a manner that prevents collapse of the tongue and/or soft palate during sleep. More specifically, the appliance may induce a reversible current or currents in a lateral direction across the tongue in a manner that shortens the patient&#39;s Palatoglossus muscle, which in turn pulls the patient&#39;s soft palate downward towards a base of the tongue, and/or decreases a volume of the tongue.

TECHNICAL FIELD

The present embodiments relate generally to sleep apnea, andspecifically to non-invasive techniques for treating one or moreunderlying causes of sleep apnea.

BACKGROUND OF RELATED ART

Obstructive sleep apnea (OSA) is a medical condition in which apatient's upper airway is repeatedly occluded during sleep. Theserepeated occlusions of the upper airway may cause sleep fragmentation,which in turn may result in sleep deprivation, daytime tiredness, andmalaise. More serious instances of OSA may increase the patient's riskfor stroke, cardiac arrhythmias, high blood pressure, and/or otherdisorders.

OSA may be characterized by the tendency of the soft tissues of theupper airway to collapse during sleep, thereby occluding the upperairway. More specifically, OSA is typically caused by the collapse ofthe patient's soft palate and/or by the collapse of the patient's tongue(e.g., onto the back of the pharynx), which in turn may obstruct normalbreathing.

There are many treatments available for OSA including, for example,surgery, constant positive airway pressure (CPAP) machines, and theelectrical stimulation of muscles associated with moving the tongue.Surgical techniques include tracheotomies, procedures to remove portionsof a patient's tongue and/or soft palate, and other procedures that seekto prevent collapse of the tongue into the back of the pharynx. Thesesurgical techniques are very invasive. CPAP machines seek to maintainupper airway patency by applying positive air pressure at the patient'snose and mouth. However, these machines are uncomfortable and may havelow compliance rates.

Some electrical stimulation techniques seek to prevent collapse of thetongue into the back of the pharynx by causing the tongue to protrudeforward (e.g., in an anterior direction) during sleep. For one example,U.S. Pat. No. 4,830,008 to Meer discloses an invasive technique in whichelectrodes are implanted into a patient at locations on or near nervesthat stimulate the Genioglossus muscle to move the tongue forward (e.g.,away from the back of the pharynx). For another example, U.S. Pat. No.7,711,438 to Lattner discloses a non-invasive technique in whichelectrodes, mounted on an intraoral device, electrically stimulate theGenioglossus muscle to cause the tongue to move forward duringrespiratory inspiration. In addition, U.S. Pat. No. 8,359,108 toMcCreery teaches an intraoral device that applies electrical stimulationto the Hypoglossal nerve to contract the Genioglossus muscle, which asmentioned above may prevent tongue collapse by moving the tongue forwardduring sleep.

Moving a patient's tongue forward during sleep may cause the patient towake, which is not desirable. In addition, existing techniques forelectrically stimulating the Hypoglossal nerve and/or the Genioglossusmuscle may cause discomfort and/or pain, which is not desirable.Further, invasive techniques for electrically stimulating theHypoglossal nerve and/or the Genioglossus muscle undesirably requiresurgery and introduce foreign matter into the patient's tissue, which isundesirable.

Thus, there is a need for a non-invasive treatment for OSA that does notdisturb or wake-up the patient during use.

SUMMARY

This Summary is provided to introduce in a simplified form a selectionof concepts that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tolimit the scope of the claimed subject matter.

A method and apparatus for reducing the occurrence and/or severity of abreathing disorder, such as OSA, are disclosed herein. In accordancewith the present embodiments, a non-invasive and removable oralappliance is disclosed that may provide electrical stimulation to alateral and/or sublingual portion of a patient's oral cavity (mouth) ina manner that prevents a collapse of the patient's tongue and/or softpalate during sleep without disturbing (e.g., without waking) thepatient. For at least some embodiments, an electric current induced bythe appliance may stimulate the patient's Palatoglossus muscle in amanner that causes the Palatoglossus muscle to stiffen and shorten,which in turn may pull the patient's soft palate and/or palatal archesin a downward direction towards a base of the patient's tongue so as toprevent the soft palate from collapsing and/or from flapping against theback of the patient's throat. Stiffening and/or shortening thePalatoglossus muscle may also cause the patient's tongue to contractand/or stiffen in a manner that prevents collapse of the tongue in aposterior direction (e.g., towards the patient's pharynx). In addition,stimulating the Palatoglossus muscle using techniques described hereinmay also lower a superior surface of the tongue T, thereby causing thetongue to cinch downward (e.g., to “hunker down”) in a manner thatfurther prevents obstruction of the patient's upper airway. Bysimultaneously preventing collapse of the patient's soft palate andtongue, patency of the patient's upper airway may be maintained in anon-invasive manner. For some embodiments, the appliance may stimulatethe patient's Palatoglossus muscle without moving the patient's tonguein an anterior direction. For at least one embodiment, stimulation ofthe patient's Palatoglossus muscle may also elevate a posterior portionof the patient's tongue, which in turn may further prevent collapse ofthe tongue onto the back of the patient's pharynx.

BRIEF DESCRIPTION OF THE DRAWINGS

The present embodiments are illustrated by way of example and are notintended to be limited by the figures of the accompanying drawings,where like reference numerals refer to corresponding parts throughoutthe drawing figures.

FIG. 1A is a side sectional view depicting a patient's upper airway.

FIG. 1B is a front plan view of the patient's oral cavity.

FIG. 1C is an elevated sectional view of the patient's tongue.

FIG. 1D is a side sectional view of the patient's tongue.

FIG. 2A is a top plan view of an oral appliance, situated over apatient's teeth, in accordance with some embodiments.

FIG. 2B is an elevated perspective view of the oral appliance of FIG.2A.

FIG. 2C is a top plan view of an oral appliance, situated over apatient's teeth, in accordance with other embodiments.

FIG. 2D is an elevated perspective view of the oral appliance of FIG.2C.

FIG. 3A is a side sectional view depicting a patient's upper airwayduring disturbed breathing.

FIG. 3B is a side sectional view depicting the patient's upper airwayresponse to electrical stimulation provided in accordance with thepresent embodiments.

FIG. 4 is a block diagram of the electrical components of the oralappliance of FIGS. 2A-2B.

FIG. 5 is a circuit diagram illustrating an electrical model of thepatient's tongue.

FIG. 6 is an illustrative flow chart depicting an exemplary operation inaccordance with some embodiments.

FIG. 7A is an elevated perspective view of an oral appliance inaccordance with other embodiments.

FIG. 7B is an elevated perspective view of the oral appliance of FIG. 7Asituated over a patient's teeth.

FIG. 7C is a rear plan view of the oral appliance of FIG. 7A situatedover a patient's teeth.

FIG. 7D is a front plan view of the oral appliance of FIG. 7A situatedover a patient's teeth.

DETAILED DESCRIPTION

A non-invasive method and apparatus for treating sleep disorders, suchas obstructive sleep apnea (OSA) and/or snoring, are disclosed herein.In the following description, numerous specific details are set forth toprovide a thorough understanding of the present disclosure. Also, in thefollowing description and for purposes of explanation, specificnomenclature is set forth to provide a thorough understanding of thepresent embodiments. However, it will be apparent to one skilled in theart that these specific details may not be required to practice thepresent embodiments. In other instances, well-known circuits and devicesare shown in block diagram form to avoid obscuring the presentdisclosure. The term “coupled” as used herein means connected directlyto or connected through one or more intervening components, circuits, orphysiological matter. Any of the signals provided over various busesdescribed herein may be time-multiplexed with other signals and providedover one or more common buses. Additionally, the interconnection betweencircuit elements or software blocks may be shown as buses or as singlesignal lines. Each of the buses may alternatively be a single signalline, and each of the single signal lines may alternatively be buses,and a single line or bus might represent any one or more of a myriad ofphysical or logical mechanisms for communication between components.Further, the logic levels and timing assigned to various signals in thedescription below are arbitrary and/or approximate, and therefore may bemodified (e.g., polarity reversed, timing modified, etc) as desired.

As used herein, the term “substantially lateral direction” refers to adirection across the patient's oral cavity in which the direction'slateral components are larger than the direction's anterior-to-posteriorcomponents (e.g., a substantially lateral direction may refer to anydirection that is less than approximately 45 degrees from the lateraldirection, as defined below with respect to the drawing figures).Further, as used herein, the term “reversible current” means a currentthat changes or reverses polarity from time to time between twocontrollable voltage potentials.

To more fully understand the present embodiments, the dynamics of OSAare first described with respect to FIGS. 1A-1D, which illustrate theanatomical elements of a patient's upper airway 100 (e.g., including thenasal cavity, oral cavity, and pharynx of the patient). Referring firstto FIGS. 1A-1B, the hard palate HP overlies the tongue T and forms theroof of the oral cavity OC (e.g., the mouth). The hard palate HPincludes bone support BS, and thus does not typically deform duringbreathing. The soft palate SP, which is made of soft material such asmembranes, fibrous material, fatty tissue, and muscle tissue, extendsrearward (e.g., in a posterior direction) from the hard palate HPtowards the back of the pharynx PHR. More specifically, an anterior end1 of the soft palate SP is anchored to a posterior end of the hardpalate HP, and a posterior end 2 of the soft palate SP is un-attached.Because the soft palate SP does not contain bone or hard cartilage, thesoft palate SP is flexible and may collapse onto the back of the pharynxPHR and/or flap back and forth (e.g., especially during sleep).

The pharynx PHR, which passes air from the oral cavity OC and nasalcavity NC into the trachea TR, is the part of the throat situatedinferior to (below) the nasal cavity NC, posterior to (behind) the oralcavity OC, and superior to (above) the esophagus ES. The pharynx PHR isseparated from the oral cavity OC by the Palatoglossal arch PGA, whichruns downward on either side to the base of the tongue T.

Although not shown for simplicity, the pharynx PHR includes thenasopharynx, the oropharynx, and the laryngopharynx. The nasopharynxlies between an upper surface of the soft palate SP and the wall of thethroat (i.e., superior to the oral cavity OC). The oropharynx liesbehind the oral cavity OC, and extends from the uvula U to the level ofthe hyoid bone HB. The oropharynx opens anteriorly into the oral cavityOC. The lateral wall of the oropharynx consists of the palatine tonsil,and lies between the Palatoglossal arch PGA and the Palatopharyngealarch. The anterior wall of the oropharynx consists of the base of thetongue T and the epiglottic vallecula. The superior wall of theoropharynx consists of the inferior surface of the soft palate SP andthe uvula U. Because both food and air pass through the pharynx PHR, aflap of connective tissue called the epiglottis EP closes over theglottis (not shown for simplicity) when food is swallowed to preventaspiration. The laryngopharynx is the part of the throat that connectsto the esophagus ES, and lies inferior to the epiglottis EP.

Referring also to FIGS. 1C-1D, the tongue T includes a plurality ofmuscles that may be classified as either intrinsic muscles or extrinsicmuscles. The intrinsic muscles, which lie entirely within the tongue Tand are responsible for altering the shape of the tongue T (e.g., fortalking and swallowing), include the superior longitudinal muscle SLM,the inferior longitudinal muscle ILM, the vertical muscle VM, and thetransverse muscle TM. The superior longitudinal muscle SLM runs alongthe superior surface SS of the tongue T under the mucous membrane, andmay be used to elevate, retract, and deviate the tip of the tongue T.The inferior longitudinal muscle ILM lines the sides of the tongue T,and is attached to the Styloglossus muscle SGM. The vertical muscle VMis located along the midline of the tongue T, and connects the superiorand inferior longitudinal muscles together. The transverse muscle TMdivides the tongue at the middle, and is attached to the mucousmembranes that run along the sides of the tongue T.

The extrinsic muscles, which attach the tongue T to other structures andare responsible for re-positioning (e.g., moving) the tongue, includethe Genioglossus muscle GGM, the Hyoglossus muscle HGM, the Styloglossusmuscle SGM, and the Palatoglossus muscle PGM. The Genioglossus muscleGGM may be used to protrude the tongue T and to depress the center ofthe tongue T. The Hyoglossus muscle HGM may be used to depress thetongue T. The Styloglossus muscle SGM may be used to elevate and retractthe tongue T. The Palatoglossus muscle PGM may be used to depress thesoft palate SP and/or to elevate the back (posterior portion) of thetongue T. Referring also to FIGS. 1A and 1B, the Palatoglossus musclePGM connects the tongue T to both sides of the Palatoglossus arch PGA,and inserts into lateral posterior regions 101 of the base of the tongueT.

It is noted that all of the muscles of the tongue T, except for thePalatoglossus muscle PGM, are innervated by the Hypoglossal nerve (notshown for simplicity); the Palatoglossus muscle PGM is innervated by thepharyngeal branch of the vagus nerve (not shown for simplicity).

During awake periods, the muscles of the upper airway (as well as thehypoglossal nerve) are active and stimulated, and may maintain upperairway patency by preventing the soft palate SP from collapsing and/orby preventing the tongue T from prolapsing onto the back of the pharynxPHR. However, during sleep periods, a relative relaxed state of the softpalate SP may allow the soft palate SP to collapse and obstruct normalbreathing, while a relative relaxed state of the tongue T may allow thetongue T to move in a posterior direction (e.g., onto the back of thepharynx PHR) and obstruct normal breathing.

Accordingly, conventional electrostimulation treatments for OSAtypically involve causing the tongue T to move forward in the anteriordirection during apnea episodes so that the tongue T does not collapsein the posterior direction. More specifically, some conventionaltechniques (e.g., disclosed in U.S. Pat. Nos. 5,190,053 and 6,212,435)electrically stimulate the Genioglossus muscle to move the tongueforward in an anterior direction during apnea episodes, while otherconventional techniques (e.g., disclosed in U.S. Pat. No. 8,359,108)electrically stimulate the Hypoglossal nerve, which in turn causes thetongue to move forward in the anterior direction by innervating theGenioglossus muscle.

Unfortunately, repeatedly moving the tongue T forward (e.g., in theanterior direction) to prevent its prolapse into the back of the pharynxPHR may undesirably wake-up the patient, which defeats the very purposeof OSA treatments and may also abrade the tongue on the teeth. Indeed,electrically stimulating the relatively large Genioglossus muscle maycause discomfort or pain. In addition, because the Hypoglossal nerveinnervates every tongue muscle except the Palatoglossus muscle PGM,electrically stimulating the Hypoglossal nerve may stimulate not onlythe Genioglossus muscle GGM but also the superior longitudinal muscleSLM, the inferior longitudinal muscle ILM, the vertical muscle VM, thetransverse muscle TM, the Hyoglossus muscle HPM, and/or the Styloglossusmuscle SSM. Stimulating multiple tongue muscles at the same time, in anattempt to move the tongue forward during apnea episodes, may not onlyover-stimulate the patient's tongue muscles but may also cause thetongue T to behave erratically (e.g., repeatedly protruding andretracting). For example, simultaneously stimulating the Genioglossusmuscle GGM and the Styloglossus muscle SGM may cause the tongue T torepeatedly protrude and retract, respectively, which is likely todisturb the patient's sleep patterns or even wake-up the patient.

Applicant has discovered that OSA may be more effectively treated bytargeting the Palatoglossus muscle PGM for electrical stimulation (e.g.,rather than targeting the Genioglossus muscle GGM or the Hypoglossalnerve for electrical stimulation). More specifically, Applicant hasdiscovered that application of one or more voltage differentials acrossselected portions of the patient's lateral or sublingual tissue mayinduce a current across the tongue to electrically stimulate thePalatoglossus muscle PGM in a manner that causes the Palatoglossusmuscle PGM to shorten (e.g., to decrease its length). For at least someembodiments, the induced current may flow in a lateral direction acrossa base portion of the patient's tongue (e.g., proximate to the lateralpoints at which the Palatoglossus muscle inserts into the tongue T).Shortening the Palatoglossus muscle, using techniques described herein,may (1) stiffen and reduce the volume of the tongue T and (2) may causethe Palatoglossal arch PGA to pull down (e.g., in a downward direction)towards the base of the tongue T.

As described in more detail below, reducing the volume of the tongue Tusing techniques described herein may prevent the tongue T fromprolapsing onto the back of the pharynx PHR, and pulling down thePalatoglossal arch PGA using techniques described herein may prevent thesoft palate SP from collapsing onto the back of the pharynx PHR. Inaddition, stimulating the Palatoglossus muscle PGM using techniquesdescribed herein may also lower the superior surface SS of the tongue T,thereby causing the tongue to cinch downward (e.g., to “hunker down”) ina manner that further prevents obstruction of the patient's upperairway.

Perhaps equally important, because the present embodiments do not targeteither the Hypoglossal nerve or the Genioglossus muscle GGM forelectrical stimulation, the present embodiments may not cause the tongueT to move forward in the anterior direction during application of theelectrical stimulation, which in turn may reduce the likelihood ofundesirably waking-up the patient. Indeed, for at least someembodiments, the voltage differential may be applied across thepatient's sublingual tissues in a manner that maintains the patient'stongue in a substantially stationary position while shortening thepatient's Palatoglossus muscle PGM. In this manner, the presentembodiments may maintain a patient's upper airway patency in a subtleyet therapeutic manner. Although electrical stimulation of thePalatoglossus muscle PGM using techniques described herein is notintended to stimulate the Genioglossus muscle GGM, any inadvertentstimulation of the Genioglossus muscle GGM will be relatively small and,at most, may serve to maintain the tongue T in a substantiallystationary position.

FIGS. 2A-2B show a removable oral appliance 200 that, in accordance withat least some embodiments, may be used to treat OSA by using electricalstimulation of the Palatoglossus muscle PGM to prevent collapse,softening, or a reduction of muscle tone of the tongue T and soft palateSP into the back of the pharynx PHR or in the airway. The appliance 200is shown in FIGS. 2A-2B as including an appliance body 205 upon which anumber of electrodes 210(1)-210(2), a control circuit 220, and a powersupply 230 may be mounted (or otherwise attached to) so as to form aunitary or divisible removable device that may fit generally within apatient's oral cavity OC (see also FIGS. 1A-1B). For such embodiments,there are no components external to the patient's body, and thereforethe appliance 200 may not be associated with wires or other connectorsthat protrude from the patient's mouth or body. For some embodiments,the oral appliance 200 may be fitted over a patient's lower teeth andpositioned to fit within a sublingual portion of the patient's oralcavity OC, for example, as depicted in FIG. 2A. For other embodiments,appliance 200 may be of other suitable configurations or structures, andthe electrodes 210(1)-210(2) may be provided in other suitablepositions. For some embodiments, there may be a minor portion of theoral appliance that protrudes slightly outside the lips or mouth.

Although only two electrodes 210(1)-210(1) are shown in FIGS. 2A-2B, itis to be understood that the appliance 200 may, in other embodiments,include a greater or fewer number of electrodes. For example, in otherembodiments, the appliance 200 may include four or another number ofelectrodes 210 arranged in opposing (e.g., “X”) patterns with respect tothe patient's sublingual tissues, wherein pairs of the electrodes may beselectively enabled and disabled in a manner that alternately inducestwo or more currents across the patient's sublingual tissues. For suchother embodiments, each of such electrodes may be turned on and/or offindependently of the other electrodes, for example, to determine a pair(or more) of electrodes that, at a particular moment for the patient,correlate to optimum electrical stimulation. The determined pair ofelectrodes may be dynamically selected either by (1) directlycorrelating electrical stimulation and immediate respiratory response orby (2) indirectly using the oral appliance 200 “to look for” the lowestimpedance electrode “pair(s).” The determined electrodes may or may notbe at the ends of an “X” pattern, and may be opposing one another.

The first electrode 210(1) and/or the second electrode 210(2), which maybe formed using any suitable material and may be of any suitable sizeand/or shape, are connected to the control circuit 220 by wires 221. Thecontrol circuit 220 and electrodes 210(1)-210(2) are electricallycoupled to power supply 230 via wires 221. Note that the wires 221 maybe positioned either within or on an outside surface of the appliancebody 205, and therefore do not protrude into or otherwise contact thepatient's tongue or oral tissue. The power supply 230 may be mounted inany of several locations and may be any suitable power supply (e.g., abattery) that provides power to control circuit 220 and/or electrodes210(1)-210(2). Bi-directional gating techniques may be used to controlvoltages and/or currents within wires 221, for example, so that wires221 may alternately deliver power to electrodes 210(1)-210(2) andexchange electrical signals (e.g., sensor signals) between electrodes240(1)-240(2) and control circuit 220.

For the exemplary embodiment of FIGS. 2A-2B, the first electrode 210(1)may include or also function as a sensor 240(1), and the secondelectrode 210(2) may include or also function as a sensor 240(2), whichcould sense respiration or other functions of interest. In other words,for some embodiments, one or both of electrodes 210(1)-210(2) may alsofunction as sensors such as respiration sensors. For such embodiments,the active function of the electrodes 210(1)-210(2) may be controlledusing bi-directional gating techniques. For example, when the firstelectrode 210(1) is to function as a driven electrode, thebi-directional gating technique may connect the first electrode 210(1)to the output of a circuit such as a voltage and/or current driver(e.g., included within or associated with control circuit 220), forexample, to provide a first voltage potential at the first electrode210(1); conversely, when the first electrode 210(1) is to function asthe respiration sensor or other sensor 240(1), the bi-directional gatingtechnique may connect sensor 240(1) to the input of a circuit such as anamplifier and/or an ADC (analog to digital) converter (e.g., includedwithin or associated with control circuit 220), for example, to sense arespiratory function of the patient. Similarly, when the secondelectrode 210(2) is to function as a driven electrode, thebi-directional gating technique may connect the second electrode 210(2)to the output of a circuit such as a voltage and/or current driver(e.g., included within or associated with control circuit 220), forexample, to provide a second voltage potential at the second electrode210(2); conversely, when the second electrode 210(2) is to function asthe respiration sensor or other sensor 240(2), the bi-directional gatingtechnique may connect sensor 240(2) to the input of a circuit such as anamplifier and/or an ADC (analog to digital) converter (e.g., includedwithin or associated with control circuit 220), for example, to sense arespiratory function of the patient.

The respiration sensors or other sensors 240(1)-240(2), as providedwithin or otherwise associated with the electrodes 210(1)-210(2), may beany suitable sensors that measure any physical, chemical, mechanical,electrical, neurological, and/or other characteristics of the patientwhich may indicate or identify the presence and/or absence of disturbedbreathing. These respiration sensors 240(1)-240(2) may also be used todetect snoring. For at least some embodiments, one or both of electrodes210(1)-210(2) may include electromyogram (EMO) sensors that, forexample, detect electrical activity of the muscles within, connected to,or otherwise associated with the patient's tongue T. For at least oneembodiment, one or both of electrodes 210(1)-210(2) may include amicrophone (or any other sensor to sense acoustic and/or vibrationenergy) to detect the patient's respiratory behavior. For otherembodiments, one or both of electrodes 210(1)-210(2) may include one ormore of the following non-exhaustive list of sensors: accelerometers,piezos, capacitance proximity detectors, capacitive sensing elements,optical systems, EMG sensors, etc.

For other embodiments, electrodes 210(1)-210(2) may not include anysensors. For at least one of the other embodiments, the electrodes210(1)-210(2) may continuously provide electrical stimulation to thepatient's Palatoglossus muscle PGM via the sublingual tissues. For analternative embodiment, a timer (not shown for simplicity) may beprovided on appliance body 205 or within control circuit 220 andconfigured to selectively enable/disable electrodes 210(1)-210(2), forexample, based upon a predetermined stimulation schedule. In anotherclosed-loop embodiment, the electrodes 210(1)-210(2) may be selectivelyenabled/disabled based upon one or more sources of sensor feedback fromthe patient.

For the exemplary embodiment of FIGS. 2A-2B, the first and secondelectrodes 210(1)-210(2) may be mounted on respective lateral arms205(1) and 205(2) of the body 205 of appliance 200 such that whenappliance 200 is placed within a sublingual portion of the patient'soral cavity OC, the first and second electrodes 210(1)-210(2) arepositioned on opposite sides of the posterior sublingual region 207 ofthe patient's oral cavity OC. For other embodiments, the first andsecond electrodes 210(1)-210(2) may be separate from appliance body 205but connected to respective lateral arms 205(1)-205(2), for example, soas to “float” beneath or on either side of the patient's tongue T, oralternatively oriented so as to be positioned on opposite sides of thesuperior surface of the tongue T. For some embodiments, the first andsecond electrodes 210(1)-210(2) are positioned in the posteriorsublingual region 207 of the oral cavity OC such that at least a portionof each of the first and second electrodes 210(1)-210(2) is proximal toa molar 209 of the patient. In this manner, the first and secondelectrodes 210(1)-210(2) may be in physical contact with the patient'ssublingual tissues proximate to the lateral posterior regions 101 atwhich the Palatoglossus muscle PGM inserts into the tongue T (see alsoFIGS. 1A-1B). Further, as depicted in FIGS. 2A-2B, the first and secondelectrodes 210(1)-210(2) may be angularly oriented with respect to thefloor of the mouth such that the first and second electrodes210(1)-210(2) substantially face and/or contact opposite sides of thetongue T proximate to the lateral posterior regions 101 at which thePalatoglossus muscle PGM inserts into the tongue T (see also FIGS.1A-1B). For other embodiments, the first and second electrodes210(1)-210(2) may be provided in one or more other positions and/ororientations.

The control circuit 220 may provide one or more signals to the first andsecond electrodes 210(1)-210(2) to create a voltage differential acrossthe patient's sublingual tissues (e.g., across the base of the tongue)in the lateral direction. For purposes of discussion herein, the firstelectrode 210(1) may provide a first voltage potential V1, and thesecond electrode 210(2) may provide a second voltage potential V2. Thevoltage differential (e.g., V2−V1) provided between the first and secondelectrodes 210(1)-210(2) may induce a current 201 in a substantiallylateral direction across the patient's sublingual tissues. For someembodiments, the current 201 is induced in a substantially lateraldirection across the patient's tongue. The current 201, which for someembodiments may be a reversible current (as described in more detailbelow), electrically stimulates the patient's Palatoglossus muscle PGMin a manner that shortens the Palatoglossus muscle PGM.

When the Palatoglossus muscle PGM is stimulated and/or shortened inresponse to the current 201 induced by the first and second electrodes210(1)-210(2), the Palatoglossus muscle PGM causes the tongue T tostiffen in a manner that decreases the tongue's volume, and that mayalso slightly cinch a portion of the tongue T closer to the floor of theoral cavity OC. One or more of decreasing the tongue's volume andslightly cinching the tongue T downward towards the floor of the oralcavity OC may prevent the tongue T from prolapsing onto the back of thepharynx PHR, thereby maintaining patency of the patient's upper airway(e.g., without moving the tongue forward in the anterior direction). Theshortening of the Palatoglossus muscle PGM may also pull the patient'sPalatoglossal arch PGA in a downward direction towards the base of thetongue T, which in turn may prevent the soft palate SP from collapsingand obstructing the patient's upper airway.

For example, FIG. 3A shows a side view 300A of a patient depicting thecollapse of the patient's tongue T and soft palate SP in a posteriordirection towards the back of the pharynx (PHR) during disturbedbreathing. As depicted in FIG. 3A, the patient's upper airway isobstructed by the tongue T prolapsing onto the back wall of the pharynxPHR and/or by the soft palate SP collapsing onto the back wall of thepharynx PHR.

In contrast, FIG. 3B shows a side view 300B of the patient depicting thepatient's upper airway response to electrical stimulation provided inaccordance with the present embodiments. More specifically, electricalstimulation provided by one or more embodiments of the appliance 200 maycause the Palatoglossus muscle PGM to stiffen and shorten, which in turnmay pull the patient's soft palate SP and/or palatal arches in adownward direction, thereby preventing the soft palate SP fromcollapsing onto the back wall of the pharynx PHR. In addition,stiffening and/or shortening the Palatoglossus muscle PGM may also causethe patient's tongue T to contract and/or cinch downward in a mannerthat prevents collapse of the tongue T towards the back of the pharynxPHR without substantially moving the tongue T forward in the anteriordirection.

The control circuit 220 may be any suitable circuit or device (e.g., aprocessor) that causes electrical stimulation energy to be provided toareas proximate to the base of the patient's tongue T via the electrodes210(1)-210(2). More specifically, the control circuit 220 may generateone or more voltage waveforms that, when provided as signals and/ordrive signals to the first and second electrodes 210(1)-210(2),primarily induces a current across (e.g., in a substantially lateraldirection) the sub-lingual portion of the patient's tongue T in a mannerthat causes the patient's Palatoglossus muscle PGM to shorten. Thewaveforms provided by control circuit 220 may include continuous voltagewaveforms, a series of pulses, or a combination of both. The controlcircuit 220 may be formed using digital components, analog components,or a combination of analog and digital components.

For some embodiments, the control circuit 220 may vary or modify thewaveform in a manner that induces a reversible current across thesublingual portion of the patient's tongue T (e.g., across the base ofthe tongue). Applicant has discovered that inducing a reversible currentacross the sublingual portion of the tongue T may decrease thelikelihood of patient discomfort (e.g., as compared with providing aconstant current or current in a single direction). More specifically,Applicant notes that when a current is induced in the sublingual tissuesof the patient, the sublingual tissues may experience carrier depletion,which in turn may require greater voltage differentials and/or greatercurrent magnitudes to maintain a desired level of electrical stimulationof the Palatoglossus muscle PGM. However, inducing greater voltageand/or current magnitudes to offset increasing levels of carrierdepletion may create patient discomfort. Thus, to prevent carrierdepletion of the patient's sublingual tissues, the control circuit 220may limit the duration of pulses that induce the current 201 across thesublingual tissues and/or may from time to time reverse the direction(e.g., polarity) of the current 201 induced across the patient'ssublingual tissues.

For some embodiments, control circuit 220 may generate and/ordynamically adjust the waveform and/or drive waveform provided to thefirst and second electrodes 210(1)-210(2) in response to one or moreinput signals indicative of the patient's respiratory behavior and/orinputs from other characteristics and sensing methods. The input signalsmay be provided by one or more of the sensors 240(1)-240(2) integratedwithin respective electrodes 210(1)-210(2).

For other embodiments, sensors other than the sensors 240(1)-240(2)integrated within respective electrodes 210(1)-210(2) may be used togenerate the input signals. For example, FIGS. 2C-2D show a removableoral appliance 270 in accordance with other embodiments. Appliance 270may include all the elements of the appliance 200 of FIGS. 2A-2B, plusadditional sensors 240(3)-240(4). For the exemplary embodiment of FIGS.2C-2D, the sensor 240(3) may be an oxygen saturation (O₂ sat) sensorthat provides a signal indicative of the patient's oxygen saturationlevel, and the sensor 240(4) may be a vibration sensor that provides asignal indicative of the patient's respiratory activity (as measured byvibrations detected within the patient's oral cavity). For otherembodiments, sensors 240(3)-240(4) may be other types of sensorsincluding, for example, sensors that measure air composition (especiallyO₂ and CO₂), heart rate, respiration, temperature, head position,snoring, pH levels, and others.

FIG. 4 shows a block diagram of the electrical components of anappliance 400 that is one embodiment of the appliance 200 of FIGS.2A-2B. Appliance 400 is shown to include a processor 410, a plurality ofelectrodes 210(1)-210(n), power supply 230, sensors 240, and an optionaltransceiver 420. Processor 410, which is one embodiment of the controlcircuit 220 of FIGS. 2A-2B, includes a waveform generator 411, a memory412, and a power module 413. The power supply 230, which as mentionedabove may be any suitable power supply (e.g., a battery), provides power(PWR) to processor 410. For some embodiments, the processor 410 may usepower module 413 to selectively provide power to sensors 240, forexample, only during periods of time that the sensors 240 are to beactive (e.g., only when it is desired to receive input signals fromsensors 240). Selectively providing power to sensors 240 may not onlyreduce power consumption (thereby prolonging the battery life of powersupply 230) but may also minimize electrical signals transmitted alongwires 221 to the processor 410. For other embodiments, power supply 230may provide power directly to sensors 240.

The sensors 240, which may include sensors 240(1)-240(2) of FIGS. 2A-2Band/or sensors 240(3)-240(4) of FIGS. 2C-2D, may provide input signalsto processor 410. The input signals may be indicative of the respiratorybehavior or other functions of the patient and may be used to detect thepresence and/or absence of disturbed breathing, for example, asdescribed above with respect to FIGS. 2A-2D.

The processor 410 may receive one or more input signals from sensors240, or sensors located elsewhere, and in response thereto may providesignals and/or drive signals (DRV) to a number of the electrodes210(1)-210(n). As described above, the signals and/or drive signals(e.g., voltage and/or current waveforms) generated by waveform generator411 may cause one or more of the electrodes 210(1)-210(n) toelectrically stimulate sublingual portions of the patient's oral cavityOC in a manner that shortens the patient's Palatoglossus muscle PGM.Shortening the Palatoglossus muscle PGM in response to electricalstimulation provided by one or more of the electrodes 210(1)-210(n) may(1) stiffen and reduce the volume of the tongue T, (2) may cause thetongue to cinch downward, and (3) may cause the Palatoglossal arch PGAto pull down (e.g., in a downward direction) towards the base of thetongue T. In this manner, the electrical stimulation provided by the oneor more electrodes 210(1)-210(n) may prevent the tongue T fromprolapsing onto the back of the pharynx PHR and/or may prevent the softpalate SP from collapsing onto the back of the pharynx PHR.

As mentioned above, the waveforms generated by the waveform generator411, when provided as signals and/or drive signals to the electrodes210(1)-210(n), primarily induce a current across the patient'ssub-lingual tissues in a manner that causes the patient's Palatoglossusmuscle PGM to shorten. The waveforms generated by the waveform generator411 may include continuous (analog) voltage waveforms, any number ofpulses that may vary in shape and duration as a pulse train, or thepulses may be combined to simulate an analog waveform or a combinationof both, and may be dynamically modified by the waveform generator 411.

The optional transceiver 420 may be used to transmit control information(CTL) and/or data, and/or receive control information and/or data froman external device via a suitable wired or wireless connection. Theexternal device (not shown for simplicity) may be any suitable displaydevice, storage device, distribution system, transmission system, andthe like. For one example, the external device may be a display (e.g.,to display the patient's respiratory behavior or patterns, to alert anobserver to periods of electrical stimulation, to indicate an alarm ifbreathing stops, and so on).

For another example, the external device may be a storage device thatstores any data produced by appliance 200, perhaps including thepatient's respiratory behavior, the electrical stimulation provided byappliance 200, the waveforms provided by waveform generator 411, and/orrelationships between two or more of the above. More specifically, forsome embodiments, the external device may store data for a plurality ofpatients indicating, for example, a relationship between the applicationof electrical stimulation to the patient and the patient's respiratoryresponse to such electrical stimulation, and may include otherinformation. Such relationship data for large numbers of patients may beaggregated, and thereafter used to identify trends or common componentsof OSA across various population demographics. The storage device may bea local storage device, or may be a remote storage device (e.g.,accessible via one or more means and/or networks including but notlimited to such as a wide area network (WAN), a wireless local areanetwork (WLAN), a virtual private network (VPN), and/or the Internet).The data and information may be made available and/or manipulatedlocally and/or remotely, and may be utilized immediately and/orpreserved for later utilization and/or manipulation.

Memory 412 may include a non-transitory computer-readable storage medium(e.g., one or more nonvolatile memory elements, such as EPROM, EEPROM,Flash memory, a hard drive, etc.) that may store the following softwaremodules and/or information:

-   -   a function select module to selectively switch an active        function of the electrodes 210 between an electrode mode (e.g.,        provided by one or more of electrodes 210 and a sensor mode        (e.g., provided by one or more of sensors 240);    -   a control module to selectively provide signals and/or drive        signals to the electrodes 210, for example, to induce an        electric current across a portion of the patient's oral cavity        in accordance with the present embodiments and/or to receive        input signals from the sensors 240; and    -   a data collection module to record data indicative of the        patient's respiratory or other behavior and/or to transmit such        data to an external device.

Each software module may include instructions that, when executed by theprocessor 410, may cause appliance 400 to perform the correspondingfunction. Thus, the non-transitory computer-readable storage medium ofmemory 412 may include instructions for performing all or a portion ofthe operations described below with respect to FIG. 6. The processor 410may be any suitable processor capable of executing scripts ofinstructions of one or more software programs stored in the appliance400 (e.g., within memory 412). For at least some embodiments, memory 412may include or be associated with a suitable volatile memory, forexample, to store data corresponding to the patient's respiratoryfunctions and/or corresponding to the electrical stimulation provided bythe appliance 200.

As mentioned above, the control circuit 220 may control the duration ofpulses that induce the current 201 across the patient's sublingualtissues, for example, to minimize carrier depletion within the patient'ssublingual tissues and/or may from time to time reverse the direction ofthe induced current 201, for example, to provide a zero sum drivewaveform (e.g., to minimize or preclude electrochemical activity and/orto minimize the patient's awareness of any electrical activity relatedto oral appliance 200). For at least one embodiment, the control circuit220 may select the pulse lengths based upon a resistive-capacitive (RC)time constant model of the patient's tongue T. For example, FIG. 5 showsan RC time constant model 500 of the patient's tongue T. The model 500is shown to include a capacitor C and two resistors, R1 and R2. For anexemplary embodiment, the capacitor C may be approximately 0.5 uF, theresistor R1 may be approximately 600 ohms, and the resistor R2 may beapproximately 4,000 ohms. Thus, for the exemplary embodiment, the timeconstant τ=R1*C may be a value approximately equal to 300 μs. Theresistor R2 represents minor “DC current” flow in the model, where thecurrent stabilizes at a small but non-zero value after more than 5 timeconstants or when DC is applied to the electrodes.

More specifically, Applicant has discovered that a typical patient'stongue T is most receptive to a current “pulse duration” that is equalto or shorter than a time period approximately equal to τ=R1*C≈300 μs.After the time period at 3 τ≈1 ms expires, the patient's tongue T mayexhibit an even greater increase in impedance, or perhaps experiencecarrier depletion, which in turn requires greater voltage levels tocontinue inducing the current 201 across the patient's sublingualtissues. As noted above, increasing the voltage levels to continueinducing the current 201 across the patient's sublingual tissues may notonly waste battery or wired power but also may cause discomfort (or evenpain) to the patient. Indeed, because current regulators typicallyutilize their available voltage “headroom” to increase the drive voltageand maintain a constant current flow when the load impedance increasesor when the effective drive voltage otherwise decreases, it is importantto dynamically manage the effective drive voltage provided by theelectrodes 210(1)-210(2).

The effective drive voltage may decrease when there is an increasedimpedance, or perhaps carrier depletion, in the patient's tongue, andthe drive resistance may increase when one (or both) of the electrodes210(1)-210(2) loses contact with the patient's sublingual tissues,generally causing the control circuit 220 to increase its drive voltagein an attempt to maintain a prescribed current flow. Thus, for at leastsome embodiments, the control circuit 220 may be configured to limit thedrive voltage and/or the current to levels that are known to be safe andcomfortable for the patient, even if the drive impedance becomesunusually high. In addition, the control circuit 220 may be configuredto from time to time reverse the polarity or direction of the inducedcurrent 201. The reversal of the current 201 can be performed at anytime. The timing of the reversal of current 201 may be selected suchthat there is no net transfer of charge across the patient's sublingualtissues (e.g., a zero sum waveform).

FIG. 6 is a flow chart 600 depicting an exemplary operation forproviding electrical stimulation to a patient in accordance with thepresent embodiments. Although the flow chart 600 is discussed below withrespect to appliance 200 of FIGS. 2A-2B, the flow chart 600 is equallyapplicable to other embodiments discussed herein. Prior to operation,the appliance 200 is positioned within a sublingual portion of thepatient's oral cavity, for example, so that the electrodes 210(1)-210(2)are positioned on opposite sides of the patient's tongue proximate tothe lateral posterior regions 101 at which the Palatoglossus muscle PGMinserts into the tongue T (see also FIGS. 1A-1B). Once the appliance 200is properly fitted within the patient's oral cavity, the appliance 200accepts zero or more input signals using a number of sensing circuitsprovided on or otherwise associated with appliance 200 (601). Asdiscussed above, the input signals may be indicative of the respiratorystate or other behavior of the patient, and may be derived from orgenerated by any suitable sensor. The control circuit 220 generates anumber of control and/or drive signals based on the input signals.(602).

In response to the signals and/or drive signals, the electrodes210(1)-210(2) induce a current in a lateral direction across asublingual portion of the patient's tongue (603). The current inducedacross the sublingual portion of the patient's tongue electricallystimulates the patient's Palatoglossus muscle (604). As described above,electrically stimulating the patient's Palatoglossus muscle may shortenthe Palatoglossus muscle (604A), may pull down the patient's soft palatetowards the base of the tongue (604B), may decrease the volume of thetongue (604C), and/or may prevent anterior movement of the tongue(604D).

For some embodiments, the induced current may be a reversible current.For at least one embodiment, the reversible current may be a zero-sumwaveform. For such embodiments, the control circuit 220 may from time totime reverse a polarity of the reversible current (605), and/or mayadjust the duration and/or amplitude of voltage and/or current pulsesand/or waveforms based on the RC time constant model of the patient'stongue (606).

FIGS. 7A-7D show a removable oral appliance 700 in accordance with otherembodiments. The oral appliance 700, which may be used to treat OSA byproviding electrical stimulation to a patient's sublingual tissues in amanner that causes the Palatoglossus muscle to shorten, is shown toinclude an appliance body 705 (which includes portions 705(1)-705(3), asshown in one or more of FIGS. 7A-7D) upon which electrodes210(1)-210(2), control circuit 220, and power supply 230 may be mounted(or otherwise attached to) so as to form a unitary and removable devicethat may fit entirely within a patient's oral cavity OC (see also FIGS.1A-1B). The oral appliance 700, which may operate in a similar manner asthe oral appliance 200 of FIGS. 2A-2B, includes appliance body 705instead of appliance body 205 of FIGS. 2A-2B. Specifically, appliancebody 705 includes two anchor portions 705(1)-705(2) and a support wire705(3). The anchor portions 705(1)-705(2) may be fitted over opposite orapproximately opposite molars of the patient, with the support wire705(3) connected between anchor portions 705(1)-705(2) and extendingalong the patient's gum line.

More specifically, for the exemplary embodiments described herein, thefirst electrode 210(1) may be attached to or otherwise associated withthe first anchor portion 705(1), and the second electrode 210(2) may beattached to or otherwise associated with the second anchor portion705(2). The control circuit 220 may be attached to support wire 705(3)and/or the second anchor portion 705(2), and the power supply 230 may beattached to support wire 705(3) and/or the first anchor portion 705(1)and/or the second anchor portion 705(2). Wires 221 (not shown in FIGS.7A-7D for simplicity) may be attached to or provided within the supportwire 705(3).

In the foregoing specification, the present embodiments have beendescribed with reference to specific exemplary embodiments thereof. Itwill, however, be evident that various modifications and changes may bemade thereto without departing from the broader scope of the disclosureas set forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

What is claimed is:
 1. A device configured to provide electricalstimulation to an oral cavity of a patient, the device comprising: anappliance including a body having first and second lateral arms eachterminating in a posterior-most free end; a first electrode including afirst portion directly attached to a lingual side of the posterior-mostfree end of the first lateral arm and including a second portionextending posteriorly beyond the posterior-most free end of the firstlateral arm; a second electrode including a first portion directlyattached to a lingual side of the posterior-most free end of the secondlateral arm and including a second portion extending posteriorly beyondthe posterior-most free end of the second lateral arm, wherein the firstand second electrodes are configured to be angularly oriented withrespect to a floor of the patient's mouth such that the first and secondelectrodes are adapted to face opposite lateral sides of the patient'stongue; and a control circuit coupled to the appliance and to theelectrodes, the control circuit configured to induce a current in alateral direction across the tongue via the first and second electrodesto generate the electrical stimulation.
 2. The device of claim 1,wherein at least one of the electrodes is further configured to sense arespiration function of the patient.
 3. The device of claim 2, whereinthe control circuit is further configured to: provide one or more firstsignals to the at least one of the electrodes during a first mode, theone or more first signals configured to induce the current; and receivea second signal from the at least one of the electrodes during a secondmode, the second signal indicative of the patient's respirationfunction.
 4. The device of claim 3, wherein the control circuit isfurther configured to dynamically adjust the one or more first signalsin response to the second signal.
 5. The device of claim 1, wherein theinduced current comprises one or more reversible currents configured toflow in one or more substantially lateral directions across the tongue.6. The device of claim 5, wherein at least one of the reversiblecurrents comprises a zero-sum waveform.
 7. The device of claim 5,wherein a pulse length of at least one of the reversible currents isconfigured according to a resistive-capacitive (RC) time constant modelassociated with the tongue.
 8. The device of claim 1, furthercomprising: a power supply, mounted on the appliance, to provide powerto the control circuit.
 9. The device of claim 8, wherein the appliance,the electrodes, the control circuit, and the power supply comprise aunitary device adapted to fit entirely within the patient's oral cavity.10. The device of claim 1, wherein the electrodes are configured toinduce the current by providing a voltage differential across thetongue.
 11. The device of claim 1, wherein the first and secondelectrodes are adapted to be in contact with opposite sides of thepatient's tongue proximate to lateral points at which a Palatoglossusmuscle inserts into the tongue when the appliance is inserted within theoral cavity.
 12. The device of claim 1, wherein the electrodes areresponsive to one or more signals generated by the control circuit. 13.The device of claim 1, wherein the induced current is configured toshorten the patient's Palatoglossus muscle without targeting thepatient's Hypoglossal nerve.
 14. The device of claim 1, wherein theinduced current is configured to pull the patient's Palatoglossal archin a downward direction towards a base of the tongue.
 15. The device ofclaim 1, wherein the induced current is configured to decrease a volumeof the tongue without moving the tongue in an anterior direction. 16.The device of claim 1, wherein one or more of the electrodes comprisesan electromyogram (EMG) sensor configured to detect electrical activityof muscles within or connected to the patient's tongue.
 17. The deviceof claim 1, wherein the electrical stimulation is configured to avoidtargeting a genioglossus muscle of the patient.
 18. The device of claim1, wherein the electrical stimulation is configured to avoid targeting ahypoglossal nerve of the patient.
 19. The device of claim 1, wherein thedevice is removable.
 20. The device of claim 1, wherein at least one ofthe electrodes is further configured to detect snoring in the patient.21. The device of claim 1, wherein at least a portion of each of thefirst and second electrodes is adapted to be positioned posterior to alast molar location of the patient when the appliance is inserted withinthe oral cavity.
 22. An appliance adapted to fit at least partiallywithin and configured to provide electrical stimulation to a patient'soral cavity, the appliance comprising: a body having first and secondlateral arms each terminating in a posterior-most free end; a firstelectrode including a first portion directly attached to a lingual sideof the posterior-most free end of the first lateral arm and including asecond portion extending posteriorly beyond the posterior-most free endof the first lateral arm; a second electrode including a first portiondirectly attached to a lingual side of the posterior-most free end ofthe second lateral arm and including a second portion extendingposteriorly beyond the posterior-most free end of the second lateralarm, wherein the first and second electrodes are configured to beangularly oriented with respect to a floor of the patient's mouth suchthat the first and second electrodes are adapted to contact oppositesublingual sides of the patient's tongue proximate to lateral points atwhich a Palatoglossus muscle inserts into the tongue; and a controlcircuit coupled to the appliance and to the electrodes, the controlcircuit configured to induce a current in a lateral direction across thetongue via the first and second electrodes to generate the electricalstimulation.
 23. The appliance of claim 22, wherein at least one of theelectrodes is further configured to sense a respiration function of thepatient.
 24. The appliance of claim 23, wherein the control circuit isfurther configured to: provide one or more first signals to the at leastone of the electrodes during a first mode; and receive a second signalfrom the at least one of the electrodes during a second mode, the secondsignal indicative of the patient's respiration function.
 25. Theappliance of claim 24, wherein the control circuit is further configuredto dynamically adjust the one or more first signals in response to thesecond signal.
 26. The appliance of claim 22, wherein the inducedcurrent comprises a reversible current.
 27. The appliance of claim 26,wherein the reversible current is configured to decrease a volume of thetongue.
 28. The appliance of claim 26, wherein the reversible currentcomprises a zero-sum waveform.
 29. The appliance of claim 26, wherein apulse length of the reversible current is configured according to aresistive-capacitive (RC) time constant model associated with thetongue.
 30. The appliance of claim 22, wherein the first and secondelectrodes are adapted to substantially face opposite lateral sides ofthe tongue.
 31. The appliance of claim 22, wherein the electricalstimulation is configured to target the patient's Palatoglossus muscle.32. The appliance of claim 22, wherein the electrical stimulation isconfigured to avoid targeting a hypoglossal nerve of the patient. 33.The appliance of claim 22, wherein the device is removable.
 34. Theappliance of claim 22, wherein at least one of the electrodes is furtherconfigured to detect snoring in the patient.
 35. The appliance of claim22, wherein at least a portion of each of the first and secondelectrodes is adapted to be positioned posterior to a last molarlocation of the patient when the appliance is inserted within the oralcavity.